function a_filt=lowpass(alpha,a);
%
%     Function to a filter Value using a 1st order low pass filter
%     By A. Mitchell 5/12/95
%     a( )          = unfiltered data vector
%     a_filt(i-1)   = Previous filtered value
%     a_filt(i)     = Value to be filtered
%     alpha         = Filter constant
%     Call: y=lowpass(alpha,a);
%
a_filt=[];
a_filt(1)=a(1);
for i=2:1:length(a);
    a_filt(i)=(1-alpha)*a_filt(i-1)+alpha*a(i);
end;
a_filt=a_filt';
return